Background: Iron and zinc deficiencies frequently occur together because the dietary factors that impair iron absorption also affect zinc absorption. There is no recommended daily intake for zinc in India. With stable isotopes of iron and zinc it is now possible to measure precisely iron and zinc absorption. The specific objectives are (1) To measure the bioavailability of iron and zinc from a representative Indian diet (2) To measure the change in bioavailability of iron and zinc achievable by feasible diversification of a representative Indian diet (3) to determine the tolerability of the feasible dietary modifications. Methods: The proposed program uses a cross-over design to study healthy children aged 13-15.9 years (16 boys and 16 girls) selected from residential schools. Baseline iron and zinc status will be assessed. All children will be randomly assigned to receive either the representative diet or the diversified diet. The proposed modification is the inclusion of ~ 20 mg ascorbic acid from fruits and vegetables which will be served with each meal. Children will be fed their respective diets for 5 consecutive days labeled with 57Fe (for 3 days only, two main meals) with an oral reference dose of 58Fe (with ascorbic acid) on day 4. Blood samples will be collected at baseline and on day 18. Simultaneously 67Zn will be given with the first meal and a reference dose of 70Zn injected intravenously on the same day. Urine will be collected from day 3 to day 6. Absorption will be quantitated by the relative enrichment of 57Fe and 58Fe in hemoglobin for iron or by 67Zn and 70Zn in urine for zinc using ICP-MS. The participants will then crossover to the other diet on day 19, following the same protocol. Tolerability of the diversified diet will be assessed for 6 weeks by administering a sensory evaluation questionnaire to the participants using a 5-point hedonic scale. Outcomes: This project will generate data on the absorption of iron and zinc in adolescents to provide a basis for determining the RDA's and the feasibility of dietary modification as a strategy to prevent iron and zinc deficiencies. The establishment of a long term collaboration between the stable isotope laboratories at Baylor College of Medicine and the National Institute of Nutrition to evaluate nutritional problems among children in India will be an important outcome of this project. PUBLIC HEALTH RELEVANCE: This study will provide evidence that achievable dietary changes in a very "at-risk" group, adolescents, in India can have important benefits in improving the amount of iron and zinc absorbed from the diet. Improving the intake of bioavailable minerals would be crucial to enhancing the health of the Indian population as it will improve school and work performance in both boys and girls. These benefits will lead to larger population-based studies and an enhanced understanding of using nutritional interventions in developing countries to improve health.